Using KY-040 Encoder Pushbutton | QMK | Page 1

elfin flume Dec 10, 2025, 8:05 AM

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I am making a keyboard using a Raspberry Pi Pico W as the microcontroller and a 6 row, 17 column matrix. I'm having a problem integrating the KY-040 Rotary encoder in it though. I know how to use just the encoder part, but not the pushbutton.

The issue is that the pushbutton shorts SW to GND when pressed (iirc), so I can't use it in my matrix. I think a solution could be using a GPIO pin just for the pushbutton and not connected to the matrix, but I don't know how to, or even if I can configure that in QMK.

If I can't, or the configuration is difficult, I am open to using another rotary encoder with a pushbutton I can wire into my matrix .

arctic timber Dec 10, 2025, 8:27 AM

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The "proper" way would be to use custom matrix and implement your own scanning to handle it
https://docs.qmk.fm/custom_matrix#lite
The hacky workarounds are

abuse DIP switch feature
wire pushbutton to its own dedicated row or col depending on diode direction

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Oh, it's one of these?

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Just take it off the PCB breakout and wire it up properly?

acoustic wharf Dec 10, 2025, 10:36 AM

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Yeah I don't know why they are connected like that, turn 5 pins on the encoder to 5 different and less usable pins on the board

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If you can cut the trace to the switch ground you could solder a wire directly to the encoder switch ground pin and have no problems, image from https://forum.arduino.cc/t/wiring-ky-040-rotary-encoder-button-function-into-matrix/890768

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I've seen circuits to incorporate the common ground into a matrix, but I don't know how well they work, and if you're going to use extra components you may as well just not use the unhelpful breakout board at all

elfin flume Dec 10, 2025, 2:15 PM

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Thank you. This is literally my first keyboard so the help is appreciated.

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Also, im assuming that the CLK, DT, and GND are connected to the microcontroller and the SW and its individual ground is connected into the matrix with a diode?

elfin flume Dec 10, 2025, 2:55 PM

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Anither question, Would i need to use the pullup resistors or can I just wire the encoder directly to GND, CLK, and DT?

acoustic wharf Dec 10, 2025, 3:07 PM

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elfin flume Also, im assuming that the CLK, DT, and GND are connected to the microcontroller...

You don't need the resistors. And yes if you cut the trace connecting the grounds, you would wire it like that

#Using KY-040 Encoder Pushbutton